Translating Magento 2 - Installing custom language pack(s)

Hi Craig,
Thank you for the tip. It worked, I was able to install the module but I’m still looking at creating my own langage packadges.
In the past I was able to do it for M.2.2 but for some reasons I can’t do it for M2.3.2

The procedure of creating langage packs for both M2.2 and M2.3 looks very similar.
source - https://devdocs.magento.com/guides/v2.3/config-guide/cli/config-cli-subcommands-i18n.html
So I created the following directories and files:

app/i18/mystore/en_GB for British English and analogically 
app/i18/mystore/fr_FR for French - France 
app/i18/mystore/de_DE for German - Germany

- composer.json
- registration.php
- langage.xml
- en_GB.csv
- fr_FR.csv
- de_DE.csv

Uploaded relevant files into relevant directory.

composer.json, registration.php, langage.xml, en_GB.csv to app/i18/mystore/en_GB

Finally, run the following commands:

bin/magento setup:static-content:deploy en_GB -f
bin/magento setup:upgrade
bin/magento cache:flush

But it doesn’t work.

My composer file looks as follow:

My language.xml file looks as follow:

My registration.php file looks as follow:

I would like to confirm that I’ve checked my Magento admin conf. and my locale settings are correct.
I don’t know what I’m doing wrong. It should be so simple. Probably I’m not running a correct command or missing one.
I check Magento documentation and checked so many different forums. When you have time can you please look at it?

If anyone knows what I’m doing wrong please let me know.
If anyone would like to have a go the below screenshot might be useful.

Thank you.
Pawel